Structure of a Multi-Zone Model of a Pressurized Water Reactor

The multi-zone model [1] of the reactor core is divided into zones according to high-altitude layers y(1...10), into sectors according to segments of 60° symmetry x(1...6) and into sections of a fuel assembly group within a sector according to service life z(1...4). Each high-altitude layer contains 163 elementary cells of a fuel assembly, and each symmetry sector contains 27 elementary cells [2]. The central fuel assembly is not included in any symmetry sector. Figure 1 shows a simplified diagram of the structure of the distributed model of the reactor core. Each zone structurally includes a point model of reactor kinetics that relates the neutron flux density to reactivity, a model of energy release in the fissile material that determines the amount of energy released as a result of fuel fission reactions depending on the neutron flux density, a coolant heating model, a model of heat transfer inside fuel rods that relates fuel temperature with the amount of energy released, a model of the reactivity effect from xenon poisoning, a model of the temperature effect of reactivity, a model of the power effect of reactivity , a model of the reactivity effect of the control group of reactor control and protection system, and a model of the reactivity effect of boron regulation [3, 4]. The multi-zone structure of the reactor model divides the reactor core in order to reduce the modeling error resulting from the linearization of a nonlinear object and enable implementation in a simulation environment [5].